The objective of this Phase I SBIR project is to design, develop and evaluate a wearable Muscle Fiber Excitation System (MFES) for preventing blood clot in immobilized patients during convalescence following lower limb orthopedic surgery. The MFES device will be derived from re-design of a hand-held model to comprise of specially- designed micro vibrators embedded in compartments of specially-designed adjustable limb brace. As the hand-held model, the MFES is expected to deliver excitation stimuli band 20Hz to 130Hz in a cyclic revolution. Applied to a limb, the limb slow and fast-twitch muscle fibers will b concurrently energized at each twitch frequency to recruit enervated muscle contractions. Prolonged MFES operation is expected to cause rhythmic muscle contraction and release resulting in rhythmic compression and release of blood vessels. This performance is expected to increase limb blood shift, with the spread of stimuli to distal anatomic locations prevent blood pooling. The project's long term objectives are pre-clinical and clinical studies to determine MFES efficacy contributing to clinical management to prevent peripheral blood pooling and clots due to age or illness or immobility after orthopedic surgery. In this Phase I SBIR project, we will develop prototypes of MFES from our large scale model and evaluate MFES technical performance in delivering excitation stimuli at muscle fiber twitch frequencies, the effects on blood flow and muscle electrical activities. Methods: We will provide a hand-held model to a medical doctor with research specialty in vein disease and experiments and a Physical Therapy Professor with research specialty in human performance to experiment and provide comment on MFES features as proposed, drawing from experimentation with the hand-held model. We will incorporate their clinical comments in SolidWorks engineering design of the MFES component parts, the accompanying special limb brace, and the human interface section for transmitting the micro vibration energy to the human limb. We will generate in SolidWorks, realistic solid models, (STL) of each component part. In partnership with OEM Fabricators Inc, we will use computer-aided manufacture to produce STL provided parts, and acquire the rest of the component parts. We will assemble the parts as designed to produce MFES prototypes. We will use our test jig for technical evaluation of MFES delivery of the proposed excitation stimuli by analyzing output signals from accelerometer mounted on the test jig that makes contact with the MFES. Through contract with the clinician researchers we will conduct limited proof of concept pilot human studies to: A) determine whether MFES excitation stimuli cause greater muscular electrical activities by comparing surface muscle electromyogram (SEMG) with and without stimuli delivery, and B) determine if lower limb blood flow is more due to MFES stimuli delivery by comparing blood flow before and after stimuli delivery. SEMG will be acquired with BiometricsTM surface electrodes connected to the tibia and femur muscle groups and BiometricsTM portable data acquisition system before and during MFES stimuli delivery. Blood flow data will be acquired with Hokanson's Photo and Strain Gauge plethysmograph targeting limb peripheral arteries and veins before and, 1 minute and 10 minutes after MFES excitation stimuli delivery. SEMG data will be processed to determine mean values, and blood flow data will be processed with Hokanson analysis software to determine arterial and venous indices. Repeated measures ANOVA will be used to analyze processed SEMG data to determine the effect of MFES stimulation during stimuli delivery, and the effect of MFES before and after stimuli delivery. Statistical analysis will be conducted in SPSS 13.0. Tests will be two tailed at 5% level of significance. To the best of our knowledge, this is the first time this approach has been proposed.